Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$213.58	3.132%	$220.2693	$220.27	$220.25	$220.30
Purchase #2	$139.93	7.304%	$150.1505	$150.15	$150.15	$150.20
Purchase #3	$174.85	3.288%	$180.5991	$180.60	$180.60	$180.60
Purchase #4	$162.38	6.501%	$172.9363	$172.94	$172.95	$172.90
Purchase #5	$185.97	10.525%	$205.5433	$205.54	$205.55	$205.50
Purchase #6	$191.25	4.586%	$200.0207	$200.02	$200.00	$200.00
Purchase #7	$211.39	6.597%	$225.3354	$225.34	$225.35	$225.30
7 purchase totals =	$1,279.35		$1,354.8546	$1,354.86	$1,354.85	$1,354.80